What is Modus Ponens and how does it work?

Conditions

• Requires a conditional statement of the form $A \rightarrow B$.
• Requires A to be true.
• Conclusion is B.

Reasoning, step by step

1. Identify the conditional premise: If A then B ($A \rightarrow B$).
2. Identify the affirmation of the antecedent: A is true.
3. Conclude that the consequent is true: Therefore B is true.

Example

The video illustrates Modus Ponens with a rain example: If it rains, the ground gets wet. It is raining. Therefore, the ground gets wet.

Common misconceptions

• Thinking that conclusions can be reached by random guessing; inference rules ensure conclusions follow logically.
• Assuming that if B is true, A must be true (affirming the consequent), which is not Modus Ponens.

Watch the explanation

Explore next

• Why are rules of inference necessary in logic?
• What are the components of a formal system?